I have recently installed a rough country 2.5" leveling kit on my 2012 2500 laramie and purchased the 18x9 RBP wheels with +10 mm and 5.5, but cannot decide on the tire to purchase. i don't want the tire to stick out to much and want it to fill the wheel well- i have been looking at the mickey thompson ATZ P3 35 12.5 18, any suggestions on tire fittment??

I would recommend Toyo AT2's over the Mickey Thompsons no question. They're a much better and quieter tire. A 35x12.5 is a great size to fill up the wheel well on a leveled 2500. That's the size I'd recommend. With those wheels they're barely be sticking out past your flare if any.